This is the first map ever produced that shows the global output of plant fluorescence. That means you're seeing the most realistic representation of healthy plant life across the entire face of the Earth.

This map is also a reminder of just how green our planet still is.

As part of their natural life cycle, plants convert light into energy in a process called photosynthesis. Essentially, they eat light. During this process, leaves emit a faint, reddish glow that scientists call plant fluorescence - and detecting it is a helpful way to measure the health of plants across wide patches of landscape.

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Not only did these maps confirm the obvious — that plants are much greener in the southern hemisphere in December, but greener in the northern hemisphere in July — but they could also lead to major scientific breakthroughs. Mostly, researchers hope to use these maps to further our understanding of how climate change and carbon emissions affect plants globally. Already, more missions are being planned that will continue mapping these fluorescent signals to find out how they change over time.

According to NASA:

Chlorophyll fluorescence offers a more direct window into the inner workings of the photosynthetic machinery of plants from space. "With chlorophyll fluorescence, we should be able to tell immediately if plants are under environmental stress — before outward signs of browning or yellowing of leaves become visible," said Elizabeth Middleton, a NASA Goddard-based biologist and a member of the team that created the maps.

But how exactly did the scientists manage to see this elusive red fluorescent glow from space? NASA explains:

The same mechanism that makes plants fluoresce causes a range of everyday objects — ground-up plant leaves, white shirts, jellyfish, and even blood and urine — to glow intensely under black light. However, plants fluoresce in specific parts of the blue, green, red, and far-red spectrum. Chlorophyll fluorescence from green foliage, for example, is produced at the red and far-red wavelengths.

"In plants, fluorescence is not something that you can see with your naked eye because background light overwhelms it," explained [Joanna] Joiner, the lead author of the paper. When sunlight strikes a leaf, disc-like green structures called chloroplasts absorb most of the light and convert it into carbohydrates through photosynthesis.

Chloroplasts re-emit about two percent of incoming light at longer, redder wavelengths. This re-emitted light — fluorescent light — is what the Goddard scientists measured to create their map. Fluorescence is different than bioluminescence, the chemically-driven mechanism lightning bugs and many marine species use to glow without exposure to light.

For decades, scientists have measured fluorescence in plants by exposing leaves to laser beams that, like black light, make fluorescence more apparent. Such experiments have revealed much about how certain types of plants fluoresce, but researchers have not been able to use lasers to measure the phenomenon across broad swaths of the Earth's surface.

To create their global fluorescence map, Joiner and her colleagues used a different technique. They analyzed an unusually dark section of the infrared portion of the solar spectrum embedded within a feature called a "Fraunhofer line." There is little background light at the line they focused on — at about 770 nanometers — which made it possible to distinguish the faint fluorescence signal.

Now we can realistically track how plant health changes in response to global events, such as weather disasters or pollution.